This invention relates to a method for detecting the formation of or presence of light-interacting domains supported by a medium. A particular aspect of the invention relates to a method of detecting particles or clumps of particles in a supporting medium. A more particular aspect of the invention relates to a method for detecting the occurrence of agglutination between antigens and their corresponding antibodies in conventional immunological diagnostic test procedures. Also included within the scope of the invention is a viewer for practicing the method of the invention.
A number of pathological conditions, as well as certain nonpathological states such as pregnancy, are routinely diagnosed through the application of well known principles of immunology. When the human or animal body is exposed to a foreign protein (antigen) the body's natural defense mechanism is triggered to produce an antibody corresponding to the invading antigen. When an antigen and its corresponding antibody come into contact with each other under the proper conditions, agglutination or agglomeration occurs, and a complex is formed which is generally less soluble than either the antigen or the antibody. This antigen-antibody reaction is the basis of most immunological diagnostic tests. In most tests a reagent containing a known antigen or antibody is added to a test medium containing serum or other body fluid from the patient. If agglutination is observed, conclusions can be made concerning the presence or absence of the corresponding antigen or antibody in the test medium. In order to provide an efficient diagnostic procedure, the presence or absence of agglutination in the test medium must be readily discernable. This has been a problem with many antigen-antibody systems wherein agglutination proceeds slowly or the particle size of the agglomerate is too small to be observed with the naked eye. This problem has been alleviated to some degree by adding a carrier material such as polystyrene latex to the antigen or antibody to form the known reagent. In a test procedure the use of a latexprotein reagent results in the formation of agglomerates which are larger and easier to observe. However, even when a carrier material is present, the visual observation of agglutination in the test medium is often difficult. As a result, the accuracy of many immunological diagnostic procedures depends greatly on the individual skill and experience of the technician conducting the test.
A number of devices have been developed for the purpose of detecting the formation of or presence of particles in a supporting medium. Some of these devices have particular application in the area of immunological diagnostic testing. For example, U.S. Pat. No. 3,432,268 describes a method and device for testing a suspension of agglutinable cells. The device operates by passing a simple beam of light through a continuous stream of a cell suspension as it is mixed with the reagent. If agglutination occurs, the cells are taken out of suspension and the ability of the suspension to transmit light is increased. A photometric system of the spectrophotometric or nephelometric type is used to detect changes in light transmission.
Another method using photoelectric means to detect agglutination is described in U.S. Pat. No. 3,463,614. The test medium containing reagent and test fluid is contained in the capillary tube. To detect clumping, a thin beam of light is directed transversely through the reciprocating capillary tube, and if clumps are present, modulation of the light beam occurs which is detected by a photodiode. The output voltage from the photodiode is coupled with conventional electric circuitry to provide a qualitative measure of agglutination.
Other examples of agglutination detecting methods using light modulating and light scattering techniques are found in U.S. Pat. Nos. 3,520,609 and 3,819,271, respectively.
Each of the methods described above has certain shortcomings in that either sophisticated and costly optical and electronic instrumentation are required, or interpretation of the results is difficult and/or time consuming.